Many receipt-type printers have limited color printing capability, such as printing receipts in two colors. Those individuals who desire to print multiple color bitmap graphics on this type of color-limited printer will obtain an output that is generally unacceptable in terms of quality and visual appeal. The present invention seeks to provide a method of adjusting color bitmap files, to provide visually acceptable output for the average user when the images are rendered on a printer with limited color printing capability.
The current invention includes a method of reducing the number of colors in a color bitmap file. The method reflects the discovery that when a logo or graphic is automatically or computer-reduced in color quantity, the result is often unsatisfactory to the average viewer. The method of the invention comprises a combination of programmatic and manual color reducing routines that reduces the bitmap to a smaller number of colors. The color reducing routines are arranged in two stages. A first stage of the color reducing routines automatically reduces the bitmap file to fewer than a specified number of colors. A second stage of the color reducing routines then allows the individual user to manually map the reduced color bitmap to colors supported by the printer. It has been discovered that manually reducing the file to the limited number of colors of a two-color printer will often provide an image with acceptable visual result for the viewer.
U.S. Pat. No. 6,206,504 for METHOD AND APPARATUS FOR TWO-COLOR INK JET POINT OF SALE (POS) PRINTING issued to Stephen R. Payne describes a two-color ink jet point of sale printer that includes a converter for converting full color printing commands into commands for printing in two colors: a primary color and an alternate color.